1. Field of the Invention
The present invention is generally in the field of semiconductors. More specifically, the present invention is in the field of fabrication of semiconductor transistors.
2. Background Art
Prior to the present invention, metallic diffusion barriers have been used in gate, source, and drain regions. Materials used for such diffusion barriers include titanium nitride. Such diffusion barriers, while providing useful functions, such as electrical conduction to the layers below, and providing a barrier against diffusion of subsequent undesirable materials into underlying regions when forming various regions, such as gate regions in a field effect transistor (FET) and/or in a high electron mobility transistor (HEMT) in III-Nitride technology, have presented certain disadvantages. For example, in adding such diffusion barriers, the resistance between the source/drain contacts and the source/drain regions in a FET or HEMT is increased. Such increased resistance diminishes the performance of transistors, such as current carrying capability and speed of transistors, which are specially important in III-Nitride power transistors, such as III-Nitride HEMTs.
It would be advantageous to reduce resistance between drain and source contacts and the respective underlying drain and source regions, while still using diffusion barriers, such as titanium nitride for the remaining portions of the transistors, such as part of the gates in FETs and/or HEMTs.